Find the perimeter of a rectangle that is 42 cm wide and 3 times the width.

1) Since the width of the rectangle is 42 cm, and the length is 3 times less than the width, in order to find out the length of the side of the rectangle, you need to divide the width of the rectangle by the number three: 42 cm: 3 = 14 cm. 2) The perimeter of the rectangle is equal to the sum of all its sides. Since the opposite sides of the rectangle are equal, then P = 2 * a + 2 * b. Substituting our values for the length and width of the rectangle, we find the value of the perimeter: P = 2 * 42 cm + 2 * 14 cm = 84 cm + 28 cm = 112 cm.
Answer: The perimeter of the rectangle is 112 cm.